Writing and manifolding material



Dec. 20, 1966 HARBORT WRITING AND MANIFOLDING MATERIAL Filed Aug. 20, 1965 7: (001mg wnh and "r led clay PA PER Fig.2

4 PAPER 5-5pirodlpyrun-layer counng with o cid fronted clay United States Patent 3,293,060 WRITING AND MANIFOLDING MATERIAL Ludwig Harbor-t, Hannover, Germany, assiguor to Gunther Wagner, Hannover, Germany Filed Aug. 20, 1965, Ser. No. 483,019 Claims priority, application Germany, Feb. 6, 1956, W 18,372 13 Claims. (Cl. 117--36.2)

This application is a con-tinuation-in-part of my earlier applications of the same title, Ser. No. 637,405, filed January 31, 1957 and Ser. No. 437,533, iiled March 5, 1965, both now abandoned.

This invention relates generally to writing and manifolding materials rand-is more particularly directed to what is commonly known as carbonless or noacarbon papers. The term paper is used in this context in a broad sense and includes typewriter ribbons. Conventional carbon and other such transfer paper having a wax basis sufler from the disadvantage that they are not sufiiciently clean on handling. Dirtying of the hands and clothing of a user cannot be avoided even when extreme care is taken. Great efforts have therefore been made to produce a carbonless transfer paper which would avoid this problem. Numerous patents have thus issued to manifolding materials in which two substantially colorless layers are pressed into contact to cause a color reaction during writing, ty ping or other similar operations. One basic form such materials have taken heretofore utilizes an adsorption color reaction wherein a color reactant material changes color when adsorbed on a suitable absorbent material, the reactant material being a dye intermediate such as crystal violet Lact-one or the like which is an electron donor, and the adsorbent material be-ng an inorganic sub-stance which is an acid relative to the dye intermediate so as to be an electron acceptor when in adsorption contact therewith. While such carbonl-ess transfer or mam-folding materials have been an improvement over more conventional carbon papers, they still have numerous disadvantages 'from the standpoint of shelf life, sensitivity of copies to solvents, various chemical materials and light, disagreeable odor and inability to produce multiple clearly legible copies. Attempts were made to overcome certain of these disadvantages by stabilizing the dye intermediates such as, for example, by utilizing the carbinols of the same interacted with certain ongan-ic bases and then reacting such compositions with an acid for the color formation. However, once again, difiiculties were encountered with regard to the storage stability or shelf life of such materials and their sensitivity to various relatively weak acids normally encountered during handling as well as the inherent characteristic of such mate-rials as dyes to smudge and stain the hands and clothing of a user.

A serious drawback of prior art transfer materials which employ acid in causing or inducing the color reaction is, of course, that ordinary paper does not withstand acid attack, but prolonged contact with acid results in distintergration and decomposition of the cellulose fibers which .in turn serious aifects the strength and stability of the paper and renders it brittle. For this reason, prior art transfer materials of this kind have not met with commercial success and the industry has been reluctant to adopt them.

- It is therefore a primary object of this invention to produce a manifoldi-ng material which is 'free from the foregoing, and other, disadvantages.

A further object of this invention is the provision of a manifolding material of the type described which is insensitive to conditions encountered in ordinary use and storage while providing one or many excellent copies when brought into contact with a specific acid reactant on application of writing pressure.

A further object of this invention is the provision of such manifolding material which will produce copies which are substantially stable to solvents and various chemical compositions as well as sufficiently stable to light.

Yet another objective of this invention is the provision of a manifolding material utilizing as a color reactant a chemical composition which is not a dye and which therefore will be stable having no tendency to stain the hands or clothing of a user.

Another objective of the instant invention is to provide mam-folding materials wherein the color reacting components may be carried on separate sheets of paper, in separate layers on the same sheet of paper, or wherein one of the color reactants may be carried on a typewriter ribbon or the like.

A still further object of the invention is to provide cleanly handled manifolding material producing intensely colored, clearly legible transfers even on the last of numerous multiple copies.

Other and further objects reside in the particular compositions and materials utilized and still other objects will in part be obvious and in part be pointed out as the description of the invention proceeds and as shown in the accompanying drawing wherein:

FIG. 1 is a fragmentary plan view and a cross section of a writing paper carrying both color reacting layers directly thereon, a portion of the upper layer being broken away for illustrative clarity; and

FIG. 2 is a fragmentary plan view and a cross section of two separate papers :forming a manifolding material in accordance with a modified embodiment of this inventiou.

Consistent with the above, it has now been 'found that manifolding materials utilizing a color reaction between a spiro-dipyran and acid activated clay has all of the advantages desired and none of the disadvantages of prior art materials.

The terms acid activated clay or acid activable clay are recognized expressions in the art and generally refer to clay which has bee-n heat-treated, .such as boiled, with a strong mineral acid, "for example, hydrochloric acid or sulfuric acid, to increase the surface area of the clay and to remove certain mineral constituents, as will appear more fully from Example 8. Although the acid is largely consumed during the heat treatment and excess acid is washed out from the clay after the heat treatment until only trace amounts remain, the treatment significantly increases the acidity and activity of the clay.

For the purpose of distinguishing the invention over the teachings of the prior art, it should be appreciated that the present color reaction is predicated on the formation of a color salt, to wit a pyrylium salt. By contrast, in the prior art color reactions, no color salt proper is formed, but the color is caused upon adsorption by electron displacement.

The conversion of spiro-dipyran compounds into pyrylium color salts could theoretically perhaps be effected with a number of substances exhibiting acidic reaction. From a practical point of view, it must, however, be considered that the acid is not permitted directly to contact and act on thesubstrate such as paper since, for the reasons previously advanced, this would result in the gradual disintegration of the paper. Consequently, the acid must be available in a form and lodged within a material so as to permit instantaneous reaction between the acid and the spiro-dipyran while on the other hand preventing disintegrating contact between the acid and the paper. For this reason, the employment of acid activated clay which is coated onto the paper base as proposed is an important feature of the present invention. As a result of the acid treatment, the clay which originally is slightly acidic, is thus imparted with a considerable increase of acidity. Moreover, the surface area of the clay is significantly increased which makes it eminently suitable for the reception of the pyrylium color salts.

Acid activated clay products are known in the art and marketed under various trade names as will be set forth more fully hereinbelow.

In accordance with a preferred embodiment of'the invention, the acid activated clay is subsequently enriched by the addition of a non-volatile inorganic or organic acid.

The manufacture of such manifolding materials can be effected according to any of the procedures currently known. For instance, a solution of one or more spiro-dipyrans in a non-volatile or a scarcely volatile solvent dispersed in the form of fine droplets in a suitable film mass coated on a paper with a layer containing the acid activated clay will jfllIlCfi'OIl upon exposure to appropriate local Writing pressures to provide the intensely colored product on contact of the reactants. The paper coated with the acid activated clay is shown for example at 1 in FIG. 1 with the spiro-dipyran layer coated thereon as shown at 2. Any suitable number of such sheets can be manifolded and impressed by any form of writing instrument including a typewriter, the application of pressure causing the spiro-dipyran to be transferred to, and to react with, the clay treated with the said acids in a color forming manner to produce a colored copy.

Alternatively, the two substantial-1y colorless materials can be individually supplied each on a separate sheet whereby a manifolding construction is produced to be used in an obvious manner. For example, in FIG. 2

paper coated with an acid activated clay is shown at 3 overlying a piece of neutral paper 4 coated with a layer 5 of the spiro-dipyran, the acid activated clay being disposed in juxtaposition to the spiro-dipyran layer whereby on arranging one or more sets of such sheets in manifolding relationship, application of writing pressure will cause contact and reaction, thereby forming a colored product. Obviously, these layers may be reversed with similar results.

A further use of the color reaction according to the invention for the production of a writing and manifolding material of the type desired consists in depositing the spiro-dipyrans in the form of a solution of the same in a non-volatile or scarcely volatile solvent in a porous synthetic substance coating of a neutral paper and transferring of the spiro dipyran to an underlying layer containing acid activated clay under suitable writing pressure.

Similarly, there exists the possibility of providing the spiro-dipyran in a film composed of waxes and plasticizers and transferring this film by writing pressure into contact with the 'layer containing the acid activated clay to produce the colored copy.

The spiro-dipyran dissolved in a non-volatile or scarcely volatile liquid can also be used for saturating a typewriter or the like ribbon which when used in combination with paper coated with an acid activated clay will result in the desired product.

In order to provide a better understanding of the instant inventive concept the following examples, which are to be considered merely as illustrative and not in a limiting sense, are provided:

EXAMPLE 1 1 part by weight of a 0.3% solution of spiro-dibenzopyran in chlordip-henyl is dispersed in 5 parts by weight of a 20 percent gelatose solution in Water and a paper carrying a layer of acid activated clay is coated with this emulsion. The spiro-di-benzopyra-n layer constitutes one component of the color reaction and the acid activated clay serves as the other. On application of 1 part by weight of a 0.1 percent solution of spirodi-naphthopyran is dispersed in 5 parts by weight of a 20 percent gelatose solution in water and is coated on a neutral paper. Reaction of this material with an acid activated clay as th Example 1 produces blue colored copies.

EXAMPLE 3 A neutral paper is coated with the following wax layer:

Parts by Weight Montan wax, light 5 Wax OP 5 Chlordiphenyl 4 Spiro-di-n'aphthopyran 2 Use of this material in combination with a layer containing an acid activated clay under writing pressure results in colored products of the type mentioned above.

EXAMPLE 4 The 'use of an emulsion of the following composition reacted under writing pressure with an acid activated clay produces similar results:

Parts by weight Chlordiphenyl 10 Spiro-di-naphthopyran 0.1 Polyvinyl alcohol, medium viscosity, 20 percent aqueous 20 Water 10 EXAMPLE 5 The layer containing the acid activated clay can be produced as follows:

4 Parts by weight Clay activated with hydrochloric acid 70 Methylcellu-lose, 2 percent aqueous 120 Glycerine 10 Water 40 Methanol 20 The above composition can be modified by replacing the clay treated with hydrochloric acid, for instance with a clay treated with sulfuric acid to produce similar satisfactory results.

EXAMPLE 6 Preparation of typewriter ribbons Formulation to be applied to ribbon:

. Percent 3-methyl-spiro-dinaphthopyran 5 Dibutyladipate 50 Castor oil 45 The dibutyladipate may be replaced by another suitable dicarboxylic acid ester of aliphatic alcohols such as butylbcnzyladipate, benzyloctyladipate or the like.

Percent 3-mtehyl-spiro-dinaphthopyran 6 Chlorodiphenyl 94 The concentration of the spiro-dipyran may vary between 2 10%; a preferred range is about 56%.

Suitable phthalic acid esters are, for example, phthalic acid -di(2-ethyl-hexyl) ester and butylbenzylphthalate.

Percent 5,6:5'6' dinaphtho spiro pyran acetic acid-ethyl ester 8 Butylbenzylphthalate 92 Percent 5,6:5',6'-dinaphtho spiro pyran acetic acid-n-propyl ester 4 Chlorodiphenyl 96 Suitable softeners are generally phosphoric acid esters such as tricresylphosphate, trioctylphosphate and diphenyloctylphosphate.

The spiro-dipyrans of A-E are also soluble in other non-volatile or difficultly volatile solvents or softeners.

The solutions obtained according to A through E are colorless and ribbons are impregnated therewith in known manner. The ribbons may consist of cotton, silk, nylon, Perlon or the like materials usually used for typewriter ribbons.

The ribbons are used in conjunction with an acid activated clay as described.

EXAMPLE 7 Coating of paper with a sponge-like plastic layer having incorporated therein spiro-dinaphthopyran Parts Butylstearate 20 Chlorodiphenyl 15 Color substance 5 Polymethacrylic acid resin (for example, a resin The color substance referred to under (A) and (B) above may be, for example,

(a) 3-methyl-spiro-dinaphthopyran or (b) 5,6:5,6' dinaphtho-spiro-pyran-3-acetic acid and propylester,

either alone or in admixture with other suitable color substances, as for example tris-(methylmercapto-phenyl)- carbinol.

The resins mentioned under (A) and (B) above may be replaced by other film forming compounds as, for example, polyvinyl chloride and/ or mixed polymers alone and/or in mixture with other resins to the extent that they are insoluble in the plasticizers employed.

In order to influence the film formation and the evaporation time, the volatile solvents mentioned under (A) and (B) above may be partially replaced by higher boiling solvents as, for example, isopropyl alcohol, isobutyl alcohol, butyl alcohol, ethylglycol.

The mixtures thus obtained are coated onto a substrate in conventional manner. The coating thus obtained reacts with acid activated clay upon application of inscribing pressure to form a colored pyrylium salt.

EXAMPLE 8 Preparation 0 acid activated clay and coating paper with acid activated clay layer According to the invention, a spiro-dipyran containing layer is reacted with a layer of acid activated clay coated onto a substrate such as paper. The reaction results in the formation of a colored pyrylium salt and is caused by exerting inscribing pressure, whereby the spiro-dipyran is brought into intimate contact with the pore structure of the clay exhibiting an acid reaction.

The acid activated clay layer may be provided on the same substrate as the spiro-dipyran layer or it may be anchored on a separate substrate.

To activate clay by acid treatment is not new .and has been repeatedly described in the literature. In this connection, reference is had to Encyclopedia of Chemical Technology, Kirk-Othmer, vol. 4, pp. 53-56, published by The Interscience Encyclopedia, Inc, 1949; Ullmann Enzyklopaedie der Technischen Chernie, 2nd edition, vol. 5, p. 224; vol. 2, pp. 476 through 478; and 3rd edition, vol. 4, pp. 541 through 544.

Generally, according to the prior art processes for activating clay, the clay, in slurry form, is boiled with a strong mineral acid, such as hydrochloric acid or sulfuric acid. Excess of acid is then washed out so that only trace amounts of acid remain which, however, impart the clay with an acid reaction. The clay is then dried. The acid treatment results in the removal by dissolution of the major amounts of calcium and magnesium originally contained in the clay. Minor amounts of iron and alumium are also removed. The acid treatment of the clay considerably increases the surface area of the clay and the calcium clay is thus transformed into a hydrogen clay of large surface structure. Due to the surface enlargement caused by the acid treatment, a sponge-like structure is formed containing a multitude of pores. This acid activated clay can be easily coated onto a paper base by conventional means. The acid which presumably is retained within the clay in an adsorbtive manner, immediately reacts with the spiro-dipyran without, however, having a destructive influence on the paper.

For the purposes of this invention, clays of the montmorillonite group are particularly suitable. Clays embraced by this group are generally referred to as bentonites and include, for example, nontronite, beidellite and hectorite.

The residual acid content in the clay can be determined as follows:

Determination of pH value 5 grams of the acid activated clay are shaken for 25 minutes with grams of distilled water, whereby a slurry is obtained. The pH of the slurry is then determined. The clay is suitable for the purposes of this invention if a pH in the range of 3.5-4.5 is obtained.

In most commercially available acid activated clays the residual acid content is very low. If the clay has been treated with hydrochloric acid, residual amounts of 0.02- 0.03% of HCl can usually be determined. In some commercial products, the residual acid quantity may be as high as 0.2%. Clays with acid contents of below.0.01% HCl are less suitable for the inventive purpose.

Commercially available acid activated clays are, for example, the materials Frankonit and Filtrol, the latter being marketed by Filtrol Company of Los Angeles.

Tonsil, manufactured by the German firm Siid-Chemie A. G. of Munich is also available in the United States.

In accordance with a preferred embodiment of this invention, commercially available acid activated clay is further enriched by adding minor quantities of nonvolatile acid thereto. Thus, additions of, for example, amidosulfonic acid, oxalic acid, maleic acid, sulfosalicylic acid, tetrachlorophthalic acid or aliphatic monoesters of the last mentioned acid have proved to yield superior results. The addition of such acids or esters accelerates the formation of the color salt and increases the color intensity, sharpness and fastness. The resistance to organic solvents, alkalis and exposure of the color formed is thus significantly increased.

The paper or the like substrate is coated with a layer which contains a major amount of the acid activated clay and may contain a minor amount of the usual pigments and binders and the like paper-coating substances. Generally, the coating mass will contain 50-90%, preferably 80-85%, calculated on the dry content, of acid activated clay. Calculated on the acid activated clay content, the mass may be admixed with between about 240% of a strong, non-volatile organic or inorganic acid of the nature hereinabove described. It has been established that the predominant portion of the acid which is added to the commercially available acid activated clay forms a stable addition product with the clay structure.

The coating mass should contain a hydrophilic binder compatible with the acid activated clay and is prepared in the usual manner by mixing and grinding, as is customary in the paper manufacturing industry. Suitable hydrophilic binders are, for example, polyvinyl alcohol, methylcellulose, polyvinylacetate dispersions, starch and starch derivatives. Mixtures of such binders are also suitable. The addition of the acid to the coating mass is advantageously effected as the last step after the mixing and grinding of the other ingredients.

The coating mass is applied to the paper substrate in customary manner as in known in the paper industry. In order to obtain satisfactory results, the paper should be coated with at least 6 g./ square meter of coating mass. However, the amount of coating mass on the paper may exceed 15 g./ square meter. The preferred range is 7-10 g./ square meter.

The following are formulations for the coating mass which have proved to give excellent results:

Percent Acid activated clay 85.2 Oxalic acid 2.7 Polyvinyl alcohol binders 4.8 Methyl cellulose do 1.2 Polyvinyl acetate dispersion do 6.1

The acid activated clay had been obtained by boiling a montmorillonite clay with sulfuric acid or hydrochloric acid. Excess of acid was then washed out until residual acid content of 0.02% was observed.

(B) Same formulation as in (A), except that the oxalic acid was replaced by amidosulfonic acid.

(C) Same formulation as in (A), except that the oxalic acid was replaced by maleic acid.

(D) Same formulation as in (A) ,except that the oxalic acid was replaced by sulfosalicylic acid.

(E) Same formulation as in (A), except that the oxalic acid was replaced by tetrachlorophthalic acid.

(F) Same formulation as in (A), except that the oxalic acid was replaced by tetrachlorophthalic acid monomethyl ester.

The binders of (A) may be replaced by other binding agents compatible with the acid activated clay and the respective acids.

Various tests were made to show the advantageous 8 properties of the material of this invention and to compare the same with prior inventions in this field like Balon US. Patent No. 2,755,200 and Green US. Patents Nos. 2,783,228 and 2,550,467. The following results are exemplary:

TEST ASENSITIVITY TO PERSPIRATION Colorless samples of crystal violet carbinols and spirodipyrans were treated with vinegar or a 5 percent acetic acid solution to simulate the relatively weak acid carried by perspiration on the hands of one normally using manifolding materials of the type in issue. The crystal violet carbinol materials formed a dark blue or purple dye in from one to two minutes which stained the fingers. The spiro-dipyran remainedcolorless even overnight.

TEST B-SENSITIVITY TO CARBON DIOXIDE Materials of the same type as described in Test A above were subjected to carbonated water in the form of club soda thereby simulating the carbon dioxide which would be adsorbed by such materials from the air on storage. With the crystal violet carbinol materials, on shaking the mixture, a dark blue or purple dye resulted in 5 to 10 minutes. In contrast, with the spiro-dipyran, no color was formed even overnight.

TEST C-CHARACTERISTICS OF DYES A substantially aqueous solution was made of the crystal violet carbinol materials (a small quantity of alcohol being necessary to increase the solubility sufficiently for the purpose intended), the solution being substantially colorless. A piece of silk textile was placed in the solution and heated to the boil as in'a dyeing operation. Although the solution remained colorless, the silk was stained a purple color thereby characterizing this material as a dye. In a similar test run with spirodipyrans, the silk remained colorless showing that these materials differ from a dye which is defined as a compound or mixture that can be applied to and give color to a second substance such as cloth, paper, plastic or leather. Condensed Chemical Dictionary, sixth edition, Reinhold Publishing Corporation, p. 428 (1961).

TEST DSTORAGE STABILITY (1) To demonstrate storage stability or shelf life of the crystal violet carbinol color formers, they have been (a) stabilized according to Balon US. Patent No. 2,755,200, Example 1, by stirring a mixture of crude crystal violet carbinol in isopropyl alcohol at room temperature with a commercial aqueous solution (36 percent) of benzyl trimethyl ammonium hydroxide being added and the mixture being stirred and heated to reflux temperature until discolored, the resulting solution being filtered and cooled; (b) stabilized according to Balon US. Patent No. 2,755,- 200, Example 16, by heating a mixture of stearyl amine (a commercial mixture of hexadecyl and octadecyl amines) and isopropanol until a clear solution was obtained to which was added a sample of the product resulting from (a) above and an aqueous 36 percent solution of benzyl trimethyl ammonium hydroxide, the mix- TEST ESTAINING CHARACTERISTICS (1) The materials of Test D2 were applied to the inside of a hand producing a strong blue-violet color reaction 9 from the (a) and (b) dyes and no color reaction of staining with the spiro-dipyrans.

(2) Repeating of Test E1 after the hand had been washed with a soap (pH 7-8) produced substantially the same results.

(3) The substances of Test D2 were applied to various other materials to determine the staining of dyeing characteristics. Tests were made with filter paper, cotton fabric, cotton fabric washed with a washing powder at 60 C. having a pH of 9, silk fabric, silk fabric washed with a washing powder at 60 C. having a pH of 9, nylon fabric, and nylon fabric washed with a washing powder at 60 C. having a pH of 9. In each instance the (a) and (b) materials produced a strong blue-violet color reaction almost immediately whereas no reaction was realized with the spiro-dipyrans.

The above tests all clearly show that the prior art materials according to Balon US. Patent No. 2,755,200 are quite sensitive to weak acids which would be carried by those handling these manifolding papers and which are absorbed on such papers from the atmosphere. This sensitivity results in a color reaction forming a dye which is capable of staining the hands and clothing of the user. In contrast, spiro-dipyrans are shown by the above tests to be particularly insensitive to such conditions, thereby failing to cause undesirable smudging and staining.

Further tests were made by utilizing various wax mixtures. It was demonstrated with such materials that these wax mixtures in and of themselves cannot be made colorless. The discoloration of the wax mixtures increases rapidly in storage, so that papers treated with such materials smudge at the slightest touch.

TEST F-PAPER MADE WITH DESENSITIZED WAX MIXTURES Further tests were made by utilizing various desensitized Wax mixtures. For this purpose 23.4 g. of a melt of carnauba wax and lanoline were neutralized by adding 0.6 g. of a 36 percent aqueous solution of benzyl trimethyl ammonium hydroxide. (Balon US. Patent No. 2,755,200, Examples 19 and 23.) To said melt the product (a) of Test D1 was added with stirring in small portions. The same procedure was carried out with product (b) of Test D1. A paper coated with both mixtures (a) and (b) showed deeply blue discoloration.

Even by using a triple of the above-mentioned amount benzyl trimethyl ammonium hydroxide added to the wax melt no colorless paper was received. To the wax materials were also added spiro-dipyrans. Application of the spiro-dipyran wax mixture as a coating on paper produced no discoloration at all. The other materials dissolved in the wax mixture produced a blue colored coating on the paper which darkened in time.

TEST GWAX MIXTURES AND PAPER COATED WITH A LAYER CONTAINING ACID ACTI- VATED CLAYS In order to determine the reaction of wax mixtures of the type described in Test F on paper coated With clay treated for instance with hydrochloric or sulfuric acids, respectively, applications of such mixtures were made. With the spiro-dipyran material, a bluish-green color reaction was produced which gained in intensity and became deeply blue after a few minutes. No additional color reaction was realized with the prior art materials in wax mixtures (above and beyond the blue colored reaction described in Test F).

The interaction of the material according to Green with a layer containing acid activated clays according to the instant invention does not result in a color formation (see US. Patent No. 2,672,396, p. 5, lines 15-19; US. Patent No. 2,669,503, p. 6, lines 3-8).

TEST HSMEAR TESTS Smear tests of paper coated with the prior art wax mixture or the spiro-dipyran wax mixture on papers showed 1 0 the former producing some blue reaction, dark blue within a period of at most 20 hours storage. The spiro-dipyran wax mixture strips produced no reaction to a smear test even after two days.

TEST IREACTIONS WITH VARIOUS WEAK ACIDS (1) Tests were made concerning reactions between the prior art materials and the spiro-dipyrans with the use of a 0.5 percent solution of triphenylchloromethane in methanol. In solution as well as on paper wetted with said solution, the prior art materials gave a strong color reaction whereas the spiro-dipyrans produced substantially no color reaction.

(2) Similarly, with a mixture of solutions of citric acid and oxalic acid in methanol, results comparable to those described in Test 11 were realized.

Thus, it will be seen from the above tests that the prior art car binol materials are by far more sensitive and therefore have numerous disadvantages not encountered with the spiro-dipyran materials.

TEST J-SENSITIVITY OF FRESH COPIES TO WATER, ALCOHOLS AND ACETONE (1) Fresh writing produced on copies made using material according to Green (US. Patents Nos. 2,783,228 and 2,550,467) were sprinkled with water which caused the writing to disappear immediately and not to reappear until after drying. Water had no effect on fresh writing produced according to the instant invention.

(2) Ethanol and methanol caused complete disappearance of fresh writing in the case of the prior materials without reappearance of the same after drying. Spirodipyran copies, when moistened with either of these materials, dissolved slightly; however, the Writing remained unobjectionably legible.

(3) Results similar to those immediately above were realized with acetone.

TEST KSOLVENT EFFECT ON COPIES SEVERAL DAYS OLD Writing on copies several days old runs under the in-' fluence of solvents such as in Test J during drying and becomes illegible with prior art materials whereas copies produced according -to the instant application were scarely changed by the influence of such solvents and remained legible.

TEST LACID AND ALKALI SENSITIVITY Copies produced according to the prior art procedure of Test I were neither resistant to acid nor alkali, sprinkling of fresh writing wit-h dilute potassium hydroxide causing disappearance of the same, the writing being illegible even after drying. With such materials, hydrochloric acid cannot cause reappearance of writing made to disappear by potassium hydroxide. Writing several days old similarly disappears and does not reappear after drying. With spiro-dipyrans, the writing does not disappear on moistening with hydrochloric acid and, after drying, it is even more intensive in color than in the nontreated condition. Potassium hydroxide solutions of low concentration are without influence on the writing. Higher concentrations will cause disappearance of the writing gradually, but it can be brought baoh 'by subsequent treatment with hydrochloric acid with a resulting higher color than before. This operation can be repeated several times.

TEST MSENSITIVITY TO LIGHT The rear transfer surface of a sheet formed according to the prior art teachings as set forth in Test J discolors blue-green on exposure to sunlight for several hours. ThlS discoloration becomes noticeable even in diffuse daylight after a longer exposure. In contrast, the rear transfer surface of a spiro-dipyran manifolding paper does not discolor under the effect of such light.

11 TEST N-MULTIPLE COPIES The sharpness of the letters produced with constructions according to the prior art are unsatisfactory in the case of multiple copies. In an eight copy manifold, from the sixth copy on made on a typewriter, an unclear, broad face was exhibited which rendered legibility difficult. With the spiro-dipyran manifolding material according to the instant invention (e.g. Example 3), eight or more copies of unobjectionable quality can be readily made.

It is concluded as a result of the above tests that a manifolding material made of spiro-dipyrans in accordance with the teachings of this application in combination with a clay treated with hydrochloric or sulfuric acid is stable and insensitive to conditions encountered in ordinary use and storage, and therefore is superior to materials made according to any of the basic prior art teachings. Additionally, the instant materials produce copies of better legibi'lity.

It will now be seen that there is herein provided an improved writing and manit'olding material which satisfies all of the objectives of the instant invention, and others, including many advantages of great practical utility and commercial importance.

In addition to the spiro-dipyrans which have been disclosed in the preceding Examples, the following spirodipyrans have been successfully tested for the inventive purposes. Table I which lists these compounds also indicates the color tone which is formed by the respective spiro-dipyran compounds upon contact with the acid activated clay.

Ethyl-mercapto-spiro-dinaphthopyran green. n-butyl-mercapto-spiro-dinaphthopyran green. 3-methyl n-aphtho (3-methoxy-benzo)-spiro-pyran red. 3.3'-Dichloro-spiro-dinaphthopyran violet-black. 3-propyl-spiro-dibenzopyran red. 3:butyl-spiro-dibenzopyran red. 3-methyl-spiro-benzo-naphtho-pyran red-violet.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In combination: a substrate, a first layer of acid activated clay anchored on said substrate, said acid activatedclay being enriched with a non-volatile acid and exhibiting strong acidic reaction, and a second layer superimposed on said first layer and containing as active ingredient an effective amount of a spiro-dipyran, said spiro-dipyran, upon application of inscribing pressure, forming a visible color salt on said first layer.

2. The combination of claim 1, wherein said second layer is superimposed onsaid clay layer without interposition of an intermediate layer.

3. The combination of claim 1, wherein the substrate is paper.

4. The combination of claim 1, wherein the amount of spiro-dipyran in said second layer is about between 210% by weight.

'5. The combipation of claim 1, wherein said spirodipyran is one of:

6. The combination of claim 1, wherein said second layer contains additionally a plasticizer.

7. The combination of claim 1, wherein said first layer contains additionally a non-volatile solvent.

8. The combination of claim 1, wherein the acid activated clay is a montmorillonite clay which has been activated by a strong mineral acid, a water slurry of said clay exhibiting a pH of about between 3.54.5.

9. The combination of claim 1, wherein the amount of said non-volatile acid in the acid activated clay is about between 2-10% calculated on the amount of clay.

10. The combination of claim 12, wherein said nonvolatile acid is one of:

amidosulfonic acid,

oxalic acid,

maleic acid,

sulfosalicylic acid,

tetrachlorophthalic acid, or

aliphatic monoesters of tetrachlorophthalic acid.

11. A recording and duplicating material with color reaction components which handles cleanly and is sensitive to writing presusre, comprising a paper coated with a layer containing a substantially colorless spirodipyran and a paper coated with a layer containing acid activated clay enriched with a non-volatile acid to exhibit strong acidic reaction, both said layers being brought into contact with each other on application of writing pressure without the interposition of an intermediate layer so that said spirodipyran in said first layer is transferred to said second layer and there reacts with said clay material in a color salt-forming manner to produce a colored copy.

12. In combination: a typewriter ribbon wherein a ribbon substrate is impregnated with a non-smearing loyer of an active color forming ingredient of a spirodipyran and a paper coated with acid activated clay of acid reaction and enriched with about between 240% of a non-volatile acid to produce colored writing on the paper when brought into contact with each other on application of writing pressure.

13. A recording and duplicating material comprising in combination: a first paper substrate having a coating which contains as active ingredient between about 2-10% of a spiro-dipyran, and a second paper substrate having a coating containing a major proportion of acid activated montmorillonite clay enriched with a minor proportion of a non-volatile acid to exhibit strong acidic reaction, said first and second paper substrates, when brought into contact with said coatings facing each other and upon application of inscribing pressure forming a visible color salt on said clay coating.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Thompson 23110.2 Langford 23110.2 Illner et a1. 23110.2 Shabaker 23-1102 Green et a1. 111736.2 Balon 1-1736.2 Webber et al. 11736.2

14 OTHER REFERENCES Robert C. Elderfield: Heterocyclic Compounds, v01. 2, pp. 293, 313 and 495, John Wiley and Sons, Inc., 1951. 5 Lubs: Chem. of Syn, Dyes and Pigments, Reinhold Pub., 1955, p. 677.

Kirk-Othmer: Ency. of Chemical Technology, vol. 4, pp. 53-56, Interscience Ency. Inc. 1949.

10 MURRAY KATZ, Primary Examiner. 

1. IN COMBINATION: A SUBSTRATE, A FIRST LAYER OF ACID ACTIVATED CLAY ANCHORED ON SAID SUBSTRATE, SAID ACID ACTIVATED CLAY BEING ENRICHED WITH A NON-VOLATILE ACID AND EXHIBITING STRONG ACIDIC REACTION, AND A SECOND LAYER SUPERIMPOSED ON SAID FIRST LAYER AND CONTAINING AS ACTIVE INGREDIENT AN EFFECTIVE AMOUNT OF A SPIRO-DIPYRAN, SAID SPIRO-DIPYRAN, UPON APPLICATION OF INSCRIBING PRESSURE, FORMING A VISIBLE COLOR SALT ON SAID FIRST LAYER. 